Asplenium nidus is an epiphytic species of fern in the family Aspleniaceae, native to tropical southeastern Asia, eastern Australia, Hawaii, Polynesia, Christmas Island, India, and eastern Africa. It is known by the common names bird's-nest fern (a name shared by other aspleniums) or simply nest fern. A 2015 molecular study found that Asplenium nidus is polyphyletic, meaning that some populations were not closely related to others—A. nidus from Madagascar, Vanuatu and New Guinea were more closely related to other species than each other. Hence a revision with sampling of the species across its range was required to delineate the taxon and identify cryptic species. Asplenium nidus forms large simple fronds visually similar to banana leaves, with the fronds growing to 50–150 centimetres (20–59 in) long and 10–20 centimetres (3.9–7.9 in) broad. They are light green, often crinkled, with a black midrib, and exhibit circinate vernation. Spores develop in sori on the underside of the fronds. These sori form long rows extending out from the midrib on the back of the outer part of the lamina (frond). The fronds roll back as they brown and create a massive leaf nest in the branches and trunks of trees.